PHOTODYNAMIC ACTION OF 1-METHYL ETHER RUBIADIN, A NATURAL ANTHRAQUINONE OVER Candida tropicalis BIOFILMS.

JULIANA MARIONI; JOSE LUIS CABRERA; SUSANA NUÑEZ MONTOYA; MARIA G. PARAJE

Congreso; XI CONGRESO DE MICROBIOLOGÍA GENERAL. SAMIGE.; 2015

Rubadin 1-methyl ether (RME) is a anthraquinone (AQ) isolated from the bioactive extracts of a phototoxic shrub, Heterophyllaea pustulata Hook f. (Rubiaceae), which grows in northwestern of Argentina. We have established that this AQ along with others present in the bioactive extracts of this plant, exhibit Photosensitizing properties. In this work, we assessed the in vitro antifungal activity of RME over Candida tropicalis biofilms, under darkness and irradiation in order to establish whether this effect could be photoestimulated; we also quantified the production of reactive oxygen species (ROS) and reactive nitrogen intermediate (RNI) in the two evaluated experimental conditions.RME, purified from benzenic extract, was identified by their RMN data. Biofilm quantification of C. tropicalis NCPF 3111 and C. tropicalis clinical was performed by the O?Toole & Kolter method. RME was tested at three concentrations in triplicate, under darkness and irradiation. The supernatant was used to measure O2·- production by the Nitro-Blue Tetrazolium (NBT) reaction, and RNI for nitric oxide (NO) generation by Griess reagent. The total system antioxidant capability was determined by FRAP assay and the activation of SOD by NBT assay. Amphotericin B (AMP B) was used as antifungic control.The biofilms formation of both strains was reduced by RME action only under irradiation. Thus, RME achieved a percentage reduction (%R) of approximately 81.8 ± 2.6 % on the clinical strain biofilm at the three tested concentrations, whereas on the biofilm of the reference strain only generated a 47 ±10 %R at a single concentration (15.6 μg/mL). In addition, RME was more active than AMP B (61.2 ±4.8 % at CIM). We noted that biofilms reduction is correlated with a large increase in the production of O2·- and NO. Moreover, we observed an inactive SOD and an increase in total antioxidant system.In conclusion, we demonstrated that the in vitro antifungal activity of RME against biofilms of C. tropicalis is due to the photodynamic mechanism Type I, and the activation of the total antioxidant system not allowed the complete biofilm eradication. Therefore, it would be promising evaluate the effect of consecutive periods of irradiation to eliminate the biofilms.